Interface for logged-in users to upload/download files

Question

I am setting up a site for a non-profit that would like to have a 'members' area where certain users can swap files for meetings, events, etc.

They essentially need a simple interface where they can upload/download files--one that is removed from the WordPress admin area. Some info:

• They would be uploading mostly text documents, so I am not worried about a high-capacity solution. The server I have for the website would definitely be able to handle the load
• There are about 30 members
• A secretary would look after the creation/removal of members
• It would be nice to be able to embed it into the site using some sort of plugin, but I am not against using a 3rd-party service either

The only solutions that are looking good so far are Dropbox Teams or Box.com Business, but they seem quite extreme for this organization's needs.

I also came across Wuala. I've never heard of it before, but the prices are much cheaper than the alternatives.

Does anybody have experience with this kind of problem? :)

Thanks a lot!